1. Field of the Invention
The present invention relates to an image formation apparatus, particularly to an image formation apparatus with a number of signal lines reduced by transmitting (multiplexing a plurality of signals on one signal line.
2. Description of the Related Art
FIG. 13 shows a basic system configuration of peripheral devices of the engine of a conventional image formation apparatus as a way of example. An image formation section (image formation control board inside the apparatus body) 51 is connected with a plurality of detachable (replaceable) units 52 to 58 and a large number of input/output signals. The detachable units are a developer unit 68, a fixation unit 52 or the like and provided with respective detection sections. Signals indicating that the units are detached from or attached to the apparatus body are inputted to the formation section from the detection sections. Also, detection signals are inputted thereto from the detection sections such as a sensor 59 or detecting temperature/humidity outside and inside the apparatus, a sensor 60 for detecting position/status information on a contact/release mechanism driven upon image formation and a storage medium, or a toner concentration sensor 54. A paper size sensor 55 and a sensor for a paper feeder unit 53 both have a signal line of plural bits, causing substantial increase in the number of signal lines. Also, feedback signals (not-shown) from high-voltage power supply or the like are inputted to the image formation section.
Moreover, each unit includes plural actuators such as a motor, a solenoid, or a clutch, and drivers for the actuators. An image formation control board (hereinafter, to be referred to as control board) outputs driving signals to the drivers as output signals. Along with full colorization, sophistication and multi-function of the image formation apparatus, the number of signal lines for the input signals to the detection sections and the output signals for the drivers has been increasing. The detection sections and actuators need power supply to operate in addition to detection signals or driving signals (data signals). As a result, a large number of signal lines and power supply lines are necessary to input the detection signals from the detection sections to the control board 51 and output the driving signals to the drivers from the control board which increases the size of the control board 51. Since the control board 51 is disposed in a distant position from the respective units and the detection sections, the large number of signals lines are wired for connecting them inside the apparatus, leading to preventing simplification, downsizing, and cost reduction of the apparatus.
Japanese Laid-Open Patent Application Publication No. 2002-258691 (Document 1) has disclosed an image formation apparatus which is provided with detachable expendables units each including an I/O expander connected via a serial bus. The image formation apparatus body includes a control section which identifies a kind of the expendables units according to a state of an input port of the I/O expander. Japanese Laid-Open Patent Application Publication No. 2006-218682 (Document 2 has disclosed a head data transfer apparatus which transfers serial image data and control signals via a same data signal line. The head data transfer apparatus includes a print bead data transfer device transferring a transfer clock and serial transfer data via an FPC cable to driver ICs corresponding to the respective print heads mounted on a recording head, and the driver ICs provided with a serial data latch signal generator circuit for internally generating serial data latch signals by use of a serial transfer clock as a reset signal and of serial transfer data as a serial data latch signal inverse trigger.
For firming images with the conventional image formation apparatus, it is necessary to conduct detailed control over the actuators in accordance with the state and operation of the respective units of the apparatus. In order to do so, the image formation apparatus needs to have an enormous number of signal lines for input/output to/from the image formation control board 51, which causing a problem of complicating the system of the apparatus and preventing the downsizing thereof. Further, another problem is in that in changing the system configuration of the apparatus number of input/output sons), it entails a lot of cost for preparing a new image formation control section in accordance with the changed configuration.
Moreover, the technique disclosed in the Document 1 has a problem of high production cost per unit since the IO expander in each expendables unit identifies a kind of the unit connected thereto only; therefore, it has to be provided in every expendables unit. Similarly, the technique disclosed in the Document 2 has a problem that a difficult, complex control has to be made for separation of serial image data and a control signal since both are transferred as a common data signal.